The mobile Internet Protocol (IP) enables a mobile terminal to move freely from one point of connection to another in various networks it visits along its route. In particular, the MIP protocol describes those actions that enable a mobile terminal to maintain connectivity during a handover from one access router to another access router. A typical handover of the mobile terminal, however, requires link-layer and IP-layer signaling. And during this signaling phase, the mobile terminal is unable to send or receive data packets. This time period is referred to as handoff delay. In many situations, the handoff delay may be unacceptable to support real-time, or otherwise delay sensitive network traffic. Thus, seamless mobility management techniques can be required for such services. In this regard, seamless mobility management can reduce or eliminate service interruption, packet loss and handoff delay, thus increasing the quality of service (QoS).
As will be appreciated, seamless handoff can be achieved through fast handoff and context transfer. Generic fast handoff mechanisms, however, only reduce the IP-layer signaling delays and do not address the link-layer delays. In this regard, there is currently no standardized technique to reduce the handoff delay when a mobile terminal moves from one link-layer technology to another. For example, a mobile terminal moving from a wireless local area network (WLAN) to a CDMA network still experiences latency due to physical-layer and link-layer signalling during handoff from one network to the other.
As will also be appreciated, different networks can be categorized as either fast-access networks (e.g., WLAN, WiMAX, Bluetooth, etc.) or slow-access networks (e.g., CDMA, GPRS, 1XEV-DO, etc.). Thus, when a mobile terminal roams from one network to another, four possibilities exist with respect to the access speed of the networks, namely, the mobile terminal can roam (1) from a fast-access network to another fast-access network, (2) from a slow-access network to a fast-access network, (3) from a fast-access network to a slow-access network, or (4) from a slow-access network to another slow-access network. And within roaming from a slow-access network to another slow-access network, the mobile terminal can more particularly roam (a) from one slow-access network to another of the same type of slow-access network (e.g., inter-PDSN handoff for a CDMA network), or (b) from a slow-access network to another, different type of slow-access network (e.g., from CDMA to GPRS).
Link-layer delay during MIP fast handoff is generally not a concern for mobile terminals roaming from a fast-access network to another fast-access network, or from a slow-access network to a fast-access network, since the link-layer setup for such handoffs is typically very fast (e.g., up to several hundred milliseconds). However, for mobile terminals roaming from a fast-access network to a slow-access network, or a slow-access network to another slow-access network, link-layer assistance can be beneficial to eliminate or at least decrease the delay due to link-layer set up.